A scanning electron microscope called the CD-SEM (Critical Dimension-Scanning Electron Microscope) is used as a means of measuring the line widths of semiconductor circuit patterns. With this apparatus, although the pattern width of a semiconductor circuit pattern at any location can be measured accurately with a high magnification, since such measurement is limited to narrow regions, the measurement needs to be conducted at a number of locations to evaluate the line widths of the patterns existing in a wide range of regions.
Also, since measurement with the CD-SEM is based on plane-like images obtained from an immediately upward direction, the profiles of sections usually cannot be measured during such measurement. For this reason, the sectional profiles of patterns are measured by actually machining the section of a pattern using ion beams or the like, and then observing this section through the CD-SEM or a transmission electron microscope (TEM).
As described above, the SEM-based measurement from an immediately upward direction has posed the problem that since the sample needs to be destroyed for sectional exposure, it is difficult to obtain three-dimensional information. In order to solve this problem, Japanese Patent Laid open No. 2003-148945 (and corresponding US2003/0090651) suggests measuring the three-dimensional shape of a pattern by use of both the SEM and an optical inspection apparatus. The art disclosed in that document is such that: a test pattern is measured in height by being irradiated with light, then in width and contrast by being irradiated with an electron beam, and the height of a pattern is estimated from the obtained contrast by using a correlation.
Optical inspection apparatuses are able to measure sectional shape profiles, and these apparatuses are high in throughput, compared with a scanning electron microscope. The optical inspection apparatus, however, has the problem that compared with a scanning electron microscope, the magnifications at which such measurement is possible are low and measuring accuracy on pattern width and the like is low. As disclosed in Japanese Patent Laid-open No. 2003-148945 ((US2003/0090651), therefore, it could be conceivable that an optical inspection apparatus and a scanning electron microscope could be combined to perform measurements.